As U.S.-backed coalition forces prepare for a final assault on the Islamic State de-facto capital Raqqa, there is a continuing push to expel fighters from nearby Tabqa dam.

The area is a key staging post on the Euphrates River close to the Syrian city that has long been an Islamic State stronghold. The dam is also a major security risk to people downstream, but U.S.-backed forces are denying claims by Islamic State fighters that it is in danger of collapse.

The dam complex came under mortar fire from Islamic State fighters last week, as Syrian engineers attempted to carry out urgent repairs on the four-kilometer long dam. They were forced to retreat, but did manage to open a spillway to relieve the pressure of water on the dam.

Syria analyst Kamal Alam of Britain’s Royal United Services Institute said IS fighters may be spreading fears over a collapse as a delaying tactic.

“This was foreseen for the last six or seven months. The Syrian government was very clear when it said that this could be used as a tactic, which meant they would have to delay their operations, because there was a clamor for the Syrian Arab army to go in after Raqqa.”

Tabqa has been an Islamic State stronghold since 2014 and it is believed many of its senior commanders are based there. The town is a key target of the U.S.-backed Syrian Democratic Forces (SDF) as they approach nearby Raqqa.

FILE - This photo from a video provided by the Syria Democratic Forces (SDF), shows fighters from the SDF opening fire on an Islamic State group's position, in Raqqa's eastern countryside, Syria, March 6, 2017.

Residents of villages downstream fear Islamic State could still attempt to blow up the dam.

"We are really scared about the dam. People came and said that IS were going to blow it up. If they blow it up it, we won't have any water, we will die of thirst. There won't be any more water, and that will mean death,” said Raheel Hassan Mahmoud, a resident of Bir Hussein al-Hammud village next to the dam.

Destruction of the dam by IS would also cause catastrophic flooding in towns and cities downstream, said Alam.

“Maybe as a final act of desperation, they could. Again, it goes to show what level they would go to damage civilian populations. But I don’t think there’s any indication at the moment that they will do it. I think coalition airstrikes are also a big threat. And the coordination in the air has not been so apparent in recent months.”

Militias fighting under the SDF alliance said the final assault on Raqqa will begin in the coming days.